Eighteen years after premiering Before Sunrise at the Sundance Film Festival, Richard Linklater and Julie Delpy returned to Park City on Sunday night for the premiere of Before Midnight, the third installment of the slow-burning film series. (Ethan Hawke couldn’t make it, but according to the letter he sent with Linklater, that was only fitting since the star of the series “was not Julie or [Hawke] but Father Time himself.”) Until now, little has been known about the third chapter in Jesse and Celine’s love story, which follows 2004’sBefore Sunset, other than the fact that Linklater, Hawke, and Delpy wrote the film last summer and it may or may not have been filmed in Greece, where the threesome were spotted. But the Sundance programmer who introduced the film assured audience members that despite the seemingly impossible expectations set for the threequel, Before Midnight was in fact his favorite of the addictive, once-in-a-decade movies. (If you can’t wait another minute for details, continue reading. If not, we suggest you avert your eyes from the spoilers below.)

When we last saw Jesse (Hawke) and Celine (Delpy), it seemed as though Jesse was going to miss his flight back to his wife and son after a chance re-encounter with Celine in Paris. Nine years after that scene, Jesse and Celine are still together after spending a summer in Greece with their twin daughters(!). Jesse’s son, Hank, also joined them for the vacation, but the film opens with Hank flying back to Jesse’s now ex-wife in Chicago. This good-bye sets into motion Jesse’s guilt, over abandoning his son, for the rest of the film.

Parenthood and adulthood having visibly taken their toll, he and Celine return with the twins to their Greek vacation home for one final night, all the time musing about their parental failings and existential worries in one epic, 13-minute take as they drive past ancient ruins. While friends babysit their daughters so that Celine and Jesse can enjoy one last Greek sunset alone, the couple takes a long, lazy walk down stone paths and past historic landmarks, all the while “bullshitting” about life, death, whether everlasting love exists, and whether Jesse would pick up Celine on a train if he had met her, middle-aged “mom body” and all, today. The conversation leads them back to the hotel, where they explode into the kind of ugly, hurtful, sometimes funny fight that couples tend to have. (And where, it should be noted, Delpy spends more than 10 minutes of screen time gesticulating while topless.) When they finally come to some sort of an agreement, it involves an imaginary letter from future Celine to present Celine and a time-traveling machine.

Like its predecessors, Before Midnightis wonderfully romantic and centers around meandering walks and talks in scenic European locations. But this time, its characters are no longer just longing and lusting—they are speaking and arguing about the complexities of their realized relationship. Even if you don’t findBefore Midnight to be the best installment of the series—we think it is—you will likely find it the most relatable and the most laugh-out-loud funny.

Although Linklater, Delpy, and Hawke had not always planned to make a third movie, the director told the audience after applause died down, “somewhere along the way, we realized [the characters] were still alive.” The trio holed up overseas in a room to write the script, a process that was easier in theory this time. “We know each other better, so we go straighter to the point,” said Delpy. “The first film, maybe we were a little more careful with each other about stuff we did not like. By now, we are like a dysfunctional old couple.”

“An old threesome couple,” deadpanned Linklater.

There is a nod to the writing process in the film, when Jesse discusses the third book that he’s just finished—which is also the third book to address, in one way or another, his relationship with Celine. Jesse’s lament, “This one took longer to write than the first and second combined,” sparked laughter from the audience. (The extra time seems worth it, though—the talk-y script is so strong that it could end up a best-original-screenplay Oscar contender next year, just as Before Sunset was in 2005.)

Later, Delpy drew another raucous response from the Sundance crowd after a festival-goer asked her which of her real-life qualities she had incorporated into the script. Without skipping a beat, she responded, “The capacity to argue endlessly.”

As of Tuesday morning, Before Midnight does not yet have a distributor or release date.